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Estrogen (E2, Estradiol) Values, Facts and Stats

Your body's estrogen levels reveal a lot about your current fertility, and are used to measure your response to fertility treatments. Practitioners and patients often use three terms interchangably when talking about the same thing: estrogen, estradiol, and E2.

Estrogen is the primary sex hormone that is present in women. Estrogen influences reproduction and sexual health, and affects a woman's bones. Estrogen stimulates the lining of the uterus, so that it grows and can sustain a pregnancy. And estrogen is a measure of ovarian activity - as follicles produce estrogen. So the more follicles there are, the more estrogen will be present. Estrogen is measured in pg/mL.

In a regular cycle, estrogen rises as follicles develop, then drops at ovulation, rises again during luteal phase, and then drops unless there is pregnancy.

What should my estrogen levels be during an IVF cycle?
This is pretty much a question that only your RE can answer. During a cycle, your estrogen will be checked along with an ultrasound follicle count - these two data points together will tell your RE how you're progressing, and whether and how much to tweak your stims.

Many doctors follow a broad range rule - if the level is between 150 - 500pg/nl on day eight, this is a satisfactory measure. And if it doubles about every 48 hours, follicle growth remains on track and is promising.

What estrogen level is too high?
There are no real absolute highs or lows with estrogen, because no two women will have the same measurements. estrogen varies from woman to woman, and it varies over time.

Typically, women with PCOS have high estrogen levels, and lower egg quality.

In an IVF cycle, since estrogen levels reflect the number of follicles that are growing, a quick rise in levels can mean too many follicles, or poor egg quality.

Reproductive endocrinologists each have their own guidelines on what levels they will tolerate in their patients; many will cancel cycles when estrogen levels approach (or overtake) 4,000 pg/ml.

What estrogen level is too low?
A low estrogen level means that there are not very many maturing follicles. Often times, your RE will simply increase your dose of stims to encourage more follicles to grow.

Some doctors use a long lupron protocol, which can over-suppress the ovaries. If this is the case, your RE will already have a plan in mind for your continued treatment. (In some cases, cycles get canceled if estrogen is too low for too long; in other cases, more stims can get a cycle back on track.)

What if my estrogen level is rising steadily and then shoots up?
A too-fast rise in estrogen may mean that you have too many follicles developing, and that you are at risk for OHSS (ovarian hyperstimulation syndrome). When an estrogen level rapidly increases too rapidly, your plan of care may need to change. Sometimes a doctor will cancel a cycle completely; others will retrieve the eggs but will not allow a fresh embryo transfer to take place. (In both of these cases, it is because pregnancy exacerbates the symptoms of OHSS.)

What if my estrogen level is rising steadily and then begins to fall?
If the level of estrogen falls (or levels off and fails to rise) during a cycle, this is pretty indicative of a poor response, and/or that the eggs are not of good quality.

What about non-IVF-related estrogen measures?
Too high or too low estrogen can indicate any number of issues with both men and women. When measured outside the realm of IVF, the following may be seen.